Information regarding the position of an object are of utmost importance for many technical and medical processes. While in medicine the position of individual tissue parts xe2x80x94e.g., of a tumor to be irradiated in order to be destroyed or in order to limit its growthxe2x80x94must be determined, the determination of position for input into a computer system, e.g., for xe2x80x9ccyber spacexe2x80x9d applications, is of general importance. Such a position determination or position input unit also is referred to in these applications as, e.g., a three-dimensional mouse. Reference is made in this context to publications U.S. Pat. No. 4, 737, 794, U.S. Pat. No. 4, 945, 305 and U.S. Pat. No. 5, 453, 686.
A medical application isxe2x80x94as mentionedxe2x80x94the treatment of tumors in the human body, whereby the tumor is irradiated with photon or, in special cases, with proton beams. The objective of such a radiation treatment is that only the tissue part forming the tumor is irradiated. Damage to the tissue surrounding the tumor is supposed to be as little as possible. Attempts to achieve this requirement are made by adapting the dose distribution of the applied beam as accurately as possible to the tumor volume or limiting it to the tumor site.
Different methods are known both for photon and proton. irradiation, whereby in some cases significant differences in quality among the various methods exist. With all of these known methods it is presupposed thatxe2x80x94while preventing damage to healthy tissuexe2x80x94a tumor position, once diagnosed, will remain constant over the treatment period.
In some cases, remarkable successes were achieved in the treatment of stationary tumors. In particular, the treatment of eye background melanomas with proton beams was found to be extremely successful.
In contrast, tumors in the thoracic and abdominal area are generally not stationary. Rather, their position constantly changes due to natural movement processes, e.g., respiration, heart contractions, peristaltics, etc.
If similar successful treatment results are to be achieved as those in stationary tumors, the tumor location must be accurately known during treatment.
For this reason, a paper by K. Ohara et al., titled xe2x80x9cIrradiation Synchronized With Respiration Gatexe2x80x9d (International Journal on Radiation Oncology Biology Physics, 1989, Vol. 17, pp. 853-857), suggested a real-time simulation of the tumor position, whereby the basis of the simulation was the deformation of the body surface, in particular the deformation due to respiratory movement. However, this method is characterized by inaccuracies, since it represents, on the one hand, not a direct measurement of the tumor position, but only an indirect measurement, and, on the other hand, does not take into account the additional factors determining positionxe2x80x94such as heart contraction and intestinal peristaltics.
The invention on hand is therefore based on the objective of describing a device which makes it possible to determine the position of objects at all times.
This objective is realized by the means described in the characterizing part of claim 1. Advantageous embodiments of the invention, its use, a process, as well as an application of the process, are described in further claims.
By using the device according to the invention, the position of an object in space can be determined with extreme accuracy. The position also can be determined without any direct connection to the object.
If a miniaturized, signal-transmitting emitter unit is attached to the tumor or to a tissue part near the tumor, it is then possible by receiving these signals outside the body through receiver units to exactly calculate the tumor position at any time. Analogously, the position can also be determined by placing the receiving unit inside or near the tumor, and the emitting unit(s) outside the body. The latter arrangement has the additional advantage that the body is exposed to a lesser transmission power and thus to a lower thermal stress than is the case with the method mentioned first. Also, the transmission of the signals measured at the object, i.e., the tumor, towards the outside, as in the last mentioned arrangement, is much simpler, since a lower transmission power must be made available for this transmission than with the first method.
In medical use, the unit positioned near the object, i.e., the tumor, is implanted surgically in the patient""s body, if this is necessary. The first arrangement requires energy for emitting signals through the emitter unit, this energy being transmitted either via an external field to the emitter unit or via a wire connection between a generator unit and the emitter unit. In another embodiment of the invention, the emitter unit has its own energy supply which is therefore implanted along with it.
In the second arrangement, the above statements apply analogously, i.e., the signals received by the receiver unit(s) are transmitted via wire connections towards the outside. But in this form of realizationxe2x80x94as mentionedxe2x80x94less energy is required for transmitting the measuring signals.